1. Field of the Invention
The present invention relates to a color display apparatus that includes electroluminescence (hereinafter referred to as EL) elements and thin film transistors (hereinafter referred to as TFTs) fabricated on a substrate.
2. Description of the Related Art
Recently, color display apparatuses incorporating EL elements have been noted as color display devices, in place of the CRTs (Cathode Ray Tubes) or LCD (Liquid Crystal Display) panels.
FIG. 1 is a cross sectional view illustrating a conventional color display apparatus including EL elements and TFT elements. Referring to FIG. 1, thin film transistors are formed on an insulation substrate 2 of glass or synthetic resin. Each TFT is prepared by successively forming on the insulation substrate 2 a gate electrode 3, a gate insulation film 4, an active layer 5 having a source region 6 and a drain region 7, an interlayer insulation film 8, a source electrode 9 connected to the source region 6, a drain electrode 10 connected to the drain region 7, and a leveled insulation film 11. Each source electrode 9 is connected to the anode electrode 37 of an organic EL element. The TFT element acts as a switching element for an organic EL element.
The organic EL elements are respectively formed on the TFT elements. Each EL element is constructed by successively forming an anode electrode 37, a second hole transfer layer 36, a first hole transfer layer 35, a luminous layer 34, an electron transfer layer 33, and a cathode electrode 32. The anode electrode 37 is made of a transparent electrode of ITO (Indium Tin Oxide) connected to the source electrode of a TFT element. The second hole transfer layer 36 is made of MTDATA(4,4xe2x80x2-bis (3 methylphenylphenylamino) biphenyl). The first hole transfer layer 35 is made of TPD (4,4xe2x80x2,4xe2x80x3-tris(3-methylphenylphenylamino) triphenylamine). The electron transfer layer 33 is made of Bebq2. The cathode electrode 32 is made of MgIn (Magnesium Indium) alloy. The layers except the electrodes are made of an organic chemical compound. An EL element is formed of the respective organic layers as well as the anode electrode 37 and the cathode electrode 32.
In the EL element, holes injected from the anode electrode 37 are recombined with electrons injected from the cathode electrode 32 in the luminous layer 34. Thus, organic molecules of the luminous layer 34 are excited so that excitons are generated. In the process during which excitons disappear, the luminous layer 34 emits light. The emitted light are radiated out from the transparent anode electrode via the transparent insulation substrate 2 (in the arrow direction in FIG. 1).
In the conventional structure, in order to form images, for example, in three primary colors including R (red), G (green) and B (blue) emitted from organic EL elements, a red luminous material, a green luminous material and a blue luminous material must be selected for the luminous layers 34. For example, porphyrin-zinc complex (ZnPr) is used for red; 10 benzo [h] quinolinol-beryllium complex (Bebq2) is used for green; and azo-methine-zinc complex (AZM) is used for blue. Since the color luminous layers are separately formed by successively performing different steps, the number of fabrication steps is increased.
Moreover, since colored light emitted from each organic EL element is blocked by the TFT area formed on the substrate 2, it is difficult to obtain sufficiently bright, clear images.
The present invention is made to solve the above-mentioned problems involved in the conventional color display apparatus. It is an object of the invention to provide a color display apparatus that can realize an increased color area and clear sharp color images and can simplify the fabrication process by forming the luminous layer of an organic EL element with one type of material (or one color material).
According to the present invention, the color display apparatus comprises a substrate; thin film transistors formed on the substrate, each of the thin film transistors having a source electrode and a drain electrode; electroluminescence elements respectively formed over the thin film transistors, each of the electroluminescence elements having a cathode connected to a source electrode or drain electrode of a thin film transistor, a luminous layer, and an anode layer sequentially formed thereover; and color elements respectively arranged on the sides of anode electrodes of the electroluminescence elements.
In the color display apparatus according to the present invention, each of the color elements comprises a color filter layer formed on a transparent substrate.
Moreover, each of the color elements comprises a color filter layer through which light of a predetermined wavelength among emitted light from the luminous layer can pass.
Each of the color elements comprises a color filter layer formed on a transparent substrate, the color filter passing light of a predetermined wavelength among beams of light from the luminous layer.
In the color display apparatus defined in the present invention, the luminous layer of each of the electroluminescence elements is formed of a white luminous material; and the color filter layer includes a layer for red light through which red light within white light emitted from the luminous layer passes, a layer for green light through which green light within the white light passes and a layer for blue light through which blue light within the white light passes.
Moreover, in the color display apparatus according to the present invention, each of the color elements comprises a fluorescent light conversion layer formed on a transparent substrate.
Each of the color elements comprises a fluorescent light conversion layer for converting light from the luminous layer into light of a predetermined wavelength.
Each of the color elements may be formed of a fluorescent light conversion layer formed on a transparent substrate, for converting light from the luminous layer into light a predetermined wavelength.
The color conversion layer of fluorescent materials may be formed of a layer for red light which converts light emitted from said luminous layer into red light, a layer for green light which converts light into green light, and a layer for blue light which converts light into blue light.
In the color display apparatus according to the present invention, a color filter layer or color conversion layer acting as a color element is formed on a transparent substrate and can be bonded to an organic EL element. Moreover, since the color element requires only one kind of color emitted from the organic EL element, it is not necessary to use plural kinds of luminous materials to the luminous element layers of the organic EL element, so that the fabrication process can be simplified.
In another aspect of the present invention, each of said anode electrodes in said EL elements is shaped in a comb, mesh, or grid planer pattern.
Since light in each display pixel is emitted from the color elements arranged over the anode electrode of the EL element, the luminous or display area become larger than a conventional EL element in which the luminescent light is emitted from the substrate on which the TFTs are formed, so that brighter, clearer color image can be displayed.
In the color display of the present invention, said EL element is able to comprise an organic EL element using an organic material for the luminous layer.